http://acryan.com/sg/2-playonhd

The Mini has had positive reviews across the board.
Its primary criticism has been that it doesn't support every single media venue on the web.
ExpertReviews.co.uk doesn't seem to like it, they are alone in the assortment of reviews I've seen and after reading the reviews they posted, it is all from one person named Kat Orphanides. She fails to talk about the playon's ability to play media which is what it was designed to do, so I can safely say that the review is rubbish.

Consider WD TV:
http://www.wdc.com/en/products/wdtv/
If you have a thumb drive, you can play videos directly off the stick. The biggest problem with WDTV is that it lacks a lot of online services, but it seems to focus on the most popular ones.

If you are in the market for a pure media streamer, the Roku is probably the best bang-for-buck choice. I like GoogleTV over the Roku because it comes with a Web Browser.

There are also several tablets on the market now that use Android that are capable of playing anything (after you root them). The Kindle Fire HD is a good example. It lacks overall storage capacity, but if you have a PC, this really isn't a big issue.

Update:

I almost forgot to mention: Valve has what is basically a mini gaming rig coming out that would easily put all media players to shame.
http://www.ign.com/videos/2013/01/08/news-valve-piston-console-details-revealed